Automobile drier unit with muffler means and selectively operable air diverting means



3,367,040 SELECTIVELY J. VANI Feb. 6, 1968 AUTOMOBILE DRIER UNIT WITHMUFFLER MEANS AND OPERABLE AIR DI VERTlNG MEANS 4 Sheets-Sheet 1 FiledJune 5, 1964 Inventor JAM ES VAN 8g, w'aaaa, M90

Feb. 6, 1968 J. VANI 3,367,040

AUTOMOBILE DRIER UNIT WITH MUFFLER MEANS AND SELECTIVELY OPERABLE AIRDIVERTING MEANS 4 Sheets-Sheet 2 Filed June llll lllllill MU/ m 3 f a J::1

Inventor JAMES VAN! 35, Zlfaiimjf' Mam fl-Hrornegs Feb. 6, 1968 J. VANIAUTQMOQILE DRIER UNIT WITH MUFFLER MEANS AND SELECTIVELY 4 S N A E M G NI T R E V I D R I A E L B A R E P O iled June Feb. 6, 1968 iled June 5,

J. VANI 3,367,040

AUTOMOBILE DRIER UNIT WITH MUFFLER MEANS AND SELECTIVELY MEANS OPERABLEAIR DIVERTING 1964 4 Sheets-Sheet In? entor' JAMES VAN! 32 MW, M4 Do w)fl-ttomegfi United States Patent Ofifice 3,367,040 Patented Feb. 6, 19683,367,049 AUTOMOBILE DRIER UNIT WITH MUFFLER MEANS AND SELECTIVELYOPERABLE AIR DIVERTING MEANS James Vani, Midlothian, 111., assignor toA. J. Industries, Inc, Los Angeles, Calif, a corporation of WestVirginia Filed June 5, 1964, Ser. No. 372,879 4 Claims. (0. 34-54) Thisinvention relates to car washing apparatus and in particular to theconstruction and arrangement of dryers adapted to dry by sweepingresidual water from a rinsed car by forced air emitted from nozzlesdirected toward the sides and top of the car.

In a standard form of automated car washing equipment, the vehicle to bewashed is moved sequentially through a plurality of stations includingan initial vacuuming and steam cleaning station, a scrubbing station, arinsing station and finally a drying station at which dryers areeffective to remove almost entirely remaining films of rinsing water.The drying operation is most frequently performed by nozzles throughwhich air is forced from impeller units.

In the interest of accelerating the drying operations, particularly onbusy days when there is a heavy stream of trafiic through the washingequipment, heavy-duty electrically powered motors drive the impellerunits to deliver large quantities of air at high velocity. This, ofcourse, entails significant power requirements and also expensive motorunits, and the primary object of the present invention is to increasethe blower efiiciency thereby reducing power requirements. Specifically,this object of the invention is achieved by constructing the impellerblades to present air foil geometry at the working surface of theimpellers, and it is found that the efficiency of air emitted throughthe dryer nozzles is increased as much as 30%, making possible autilization of lower power requirements for driving the impellers.

As noted above, a significant factor entering into the design ofequipment to which the present invention relates is the density oftraflic through the washing apparatus. On busy days it is important toaccelerate drying so that an automobile or other vehicle stands in thedrying station for as short a time as possible. On the other hand, andin view of the expensive and heavy-duty power equip ment required, it isdesirable to be able to save on the expense, reducing overhead, and thispossibility is presented in those instances where the traific throughthe washing apparatus is not so heavy, that is, the number of vehicleson a particular day is sparse. Therefore, another object of the presentinvention is to enable the dryer apparatus to be varied for heavy orsparse traffic, thereby relating the rate of trafiic to overhead orexpense of operation. Another object of the invention is to provideblower units on both sides of a vehicle and relate the blower units sothat with heavy traffic each blower unit supplies air for drying oneside of a vehicle and with light trafiic one blower unit can supply airfor drying both sides of a vehicle. Specifically, this object of theinvention is accomplished or satisfied by incorporating in the dryerequipment an interrelated set of dampers such that with both dampersopen, the drying apparatus is accommodated to heavy traffic through thewashing equipment, whereas with one of the dampers closed, the dryerapparatus is accommodated to a lower rate of traffic. Furthermore, thisarrangement of dampers enables one of the blower units to be idle, andtherefore conserved while the other blower unit is operating, and byswitching back and forth no one blower unit is overly taxed.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawings which,

by way of illustration, show preferred embodiments of the presentinvention and the principles thereof and what is now considered to bethe best mode contemplated for applying these principles. Otherembodiments of the invention embodying the same or equivalent principlesmay be used and structural changes may be made as desired by thoseskilled in the art without departing from the present invention.

In the drawings:

FIG. 1 is a perspective view of a car at a drying station in anautomatic car wash line;

FIG. 2 is a front elevational view of the drying station;

FIG. 3 is a plan view of the drying station;

FIG. 4 is a side view of the drying station;

FIG. 5 is an enlarged sectional view of one side of a drying station;

FIG. 6 is a sectional view taken along the lines 66 of FIG. 5;

FIG. 7 is a perspective view of a mufiier and attached ducts;

FIG. 8 is a view of an impeller for the air blower unit;

FIG. 9 is a sectional view of the impeller blades; and

FIG. 10 is a view of the impeller scroll or housing.

Referring now to the drawings, and in first instance to the perspectivevieW of FIG. 1, there is illustrated an automobile at a drying station15 of an automatic car wash line through which the vehicle has beenpulled by a conveyor 16 having rollers 18, one being behind the wheel ofthe car. The typical automatic car wash line has an initial vacuumingstation wherein the interior of the vehicle is vacuumed; a steam andwater cleaning station wherein the car is wetted and a soap or detergentis applied; a scrubbing station wherein the car is scrubbed by brushesor the like; a rinsing station wherein water is swept across the car toremove the detergent and any remaining dirt; and finally the dryingstation 15 at which high velocity streams of air are directed along thesides of the vehicle and across the top of the vehicle to sweep therinse water rearwardly and downwardly from the vehicle. The velocity ofthe air leaving the nozzles in the present invention is in excess of 250mph. and the air is thus directed by the nozzles to sweep the water fromthe car as the car is pulled through the stationary drying station, andadditionally, the air evaporates some of the moisture from the car body.

As seen in FIGS. 1 and 2, the drying station 15 is generally a U-shapedstructure with a pair of side units or towers 20 and 21 between whichextends an overhead duct 22, which applies air to an overhead or topnozzle means 24. The side units 20 and 21 each have a side nozzle 25 and26 each of which is adapted to extend generally transverse the side ofthe car body so as to apply air across the entire sides of the vehiclebody. As seen in FIGS. 2 and 3, the top nozzle 24 is adapted to extendacross the hood of the vehicle to applying drying air thereto, and asthe windshield of the vehicle contacts a trip switch 30 disposedforwardly of the top nozzle 24, the top nozzle swings upwardly to clearthe windshield and the roof of the vehicle so as to be in position tosweep air across the roof of the vehicle without contacting thewindshield or roof.

The side units 20 and 21 are identical in construction and are eachadapted to supply air at high velocity to the top duct 22 for the topnozzle 24. In the description hereinafter, only one of the side units,namely side unit 21, is described, and the description is applicable tothe other side unit 20.

The side unit 21 has three closed and vertically extending outer sidewalls 33, 34 and 35 which extend upward from a base 36 to an open topplate 38. The side walls 33, 34 and 35 are joined to each other at abottom or base 3 36 and to a fourth side wall 40, in which is disposedthe side nozzle 26 to provide a genererally soundproof and airtightenclosure or housing. Air enters a side unit 21 or 22 through a screenedfilter 42 disposed in the opening in the top plate 38.

Disposed interiorly of the housing 41, is the muffler and duct unit 45,FIG. 7. The inlet air entering the filter 42 at the top of the unit 21or 22 passes about a curved outer wall 44 of the muffler 48 anddownwardly towards a motor 50 having a shaft 51 for driving an impeller52, FIG. 5. The motor 50 is suitably secured on a mounting block 5213fastened to the base 36. Extending upwardly from the base 36 is aninterior duct wall 55 which extends between the opposite side walls 33and 35 and is spaced from an outer duct wall 54. An annular opening 56is formed in the wall 55 opposite the motor 50 and adjacent the inner orhub portion 57 of the impeller 52 so as to permit the inlet air to bedrawn into the center and interior of the impeller 52 wherein the air isdriven by the impeller blades 58 within the confines of the impellerhousing or scroll 60, as best seen in FIG. 10. The inlet air now at highvelocity exits at opening 61 into a duct space 62 formed between theinner duct Wall 55 and the outer duct Wall 54. The impeller 52 drivesthe air upwardly through the duct 62 and into an annular opening 64 in aduct wall 55 and through an inner ring 68 of a pair of concentric ringsof the muffler 48. The mufller and duct unit 45 has an annular attachingflange 65, which is secured by suitable nut and bolt fasteners 66 to theduct wall 55, so that the opening in the inner ring 68 of the mufller 48is aligned with the opening 64 in the wall 55.

The inner mufller ring 68 is in the form of a cylindrical element havinga pair of inner and outer screen or expanded metal members 69 and 70between which is inserted a filler of fibre glass insulation or thelike. The high velocity air entering the inner ring 68 of the muffler 48exits its open and outer end 74 and is confined within an encirclingouter cylindrical member or cylinder 75, which is also secured to theattaching flange 65. The outer muflier cylinder 75' has an inner screenor expanded metal member 76 and has the outer solid or sheet metal wall44 about which the low velocity inlet air flows to the impeller 52.Between the cylindrical walls 76 and 44, there is disposed a layer ofinsulation such as fibre glass or the like. Thus, the air entering themuffler 48 at the opening 64 flows generally through the inner openingin the inner cylinder member 68 and exits the opening 74 and flowsrearwardly in the annular space between the concentric rings 68 and 75.The air leaves this annular air space through top duct opening 79 andside duct opening 80.

As best seen in FIG. 7, the mufller 48 has a side duct 82 extendinggenerally downwardly and toward the nozzle 26, to which the side duct 82is connected by a series of fasteners 83. The side duct 82 is composedof a two-part construction having a first part 84 connected to the outercylinder member 75, as by welding or the like, and a lower portion 85generally tapered and flared in construction at the portion attached bythe bolts 83. The portions 84 and 85 of the duct 82 are connected byattaching flanges 86 in which are disposed suitable nut and bolts 87.

Since the air exiting the nozzles 24, 25 and 26 is in excess of 250 mph.and in some applications has a velocity of 300 mph, the mutller 48 isadapted to dampen or choke out much of the noise or vibrations attendantwith the generation and the conveying of high velocity air through aduct system.

The vertically extending side walls 33, 34, 35 and 40 include exteriorpanel members 90, FIG. 6, having three inches of insulation 91 disposedbetween Z section reinforcing elements 92..The panels 90 are joined atthe respective four corners by corner panels 94 which are likewisefilled with three inches of insulation to reduce downwardly past theside duct 82 to the opening 56 in the duct wall 55 to the center portionof the impeller 52 and impeller housing 60, whereupon the impeller 52forces the air about the scroll 60 to exit the scroll opening 61 at ahigh velocity. The high velocity air moves upwardly through the duct 62and into the opening 64 of the inner cylindrical member 68 of themufiler 48, exits the end 74 of the inner mulfler member 68 to flowrearwardly in the annular air space. between the inner mufiler member 68and the outer muflier element to an upper duct opening 79 and a sidewall duct opening 80. The high velocity air flows through the respectiveside nozzle ducts to the respective side nozzles 25 and 26 wherein theair is directed against the sides of the automobile movingtherethroughl-ligh velocity air from each of the respective side units20 and 21 flow through the duct units toward each other and toward thetop nozzle 24 wherein the converging streams of air are directeddownwardly through the top nozzle 24 to sweep across the top of thevehicle.

With the present invention, each of the motors 50 for the side units 20and 21 is preferably a 50 horsepower motor and as can be readilyappreciated the power requirements for operation of both motorssimultaneously is quite considerable. It is an important aspect of thepresent invention that on days where the traffic movirg through the carwash line 15 and through the drying station, is relatively light, ascompared to the traflic capable of being moved through the car washsystem and the drying station in heavy traflic days. At times of lighttraffic, one of the motors 50 can be shut off and high velocity airgenerated by one of the blower units can be ducted to both side nozzles25 and 26, as well as the top nozzle 24. For this purpose, each of theside units 20 and 21 is provided with a novel damper means 100, whichpermits the blocking of the air intake for its respective side unit 20or 21 to thereby assure that the high velocity air generated by theother unit cannot escape through the air inlet and that the highvelocity air is diverted to its respective side nozzle and to the sideof the car opposite the blower unit generating the high pressure air.

The damper means 100 has a circular damper plate or flap 101 which issecured to a bar 102, the bar 102 being journaled in flange bearings 103secured on the metal housing of the muffler 48. The circular plate 101is normally positioned in a non-blocking position within the bore of thesmall cylindrical muffler 68 element and presents only a thin leadingedge to the air entering the muffler when in its non-blocking position.However, the damper means 100 is adapted to be moved to a blockingposition wherein the circular plate 101 is rotated through to a positionwherein the entire circular area of the plate 101 is disposed across thebore of the cylindrical member 68 to block movement of air entering intothe muffler 48 from flowing into the duct 62.

The damper rod 102 is rotated by actuation of an air cylinder 106 whichforces its plunger 107 outwardly of the cylinder 106 to rotate a crank108 attached to the rod 102. The air cylinder 106 is a double acting aircylinder so that when air pressure is reversed, the piston rod 107 ismoved inwardly into the cylinder 106 and causes the crank 168 to rotatethe damper flap 101 to the closed position.

It will be realized that at periods of heavy trafiic that both of thedamper flaps 101 will be open and that both blower units will besupplying air to the top nozzle 24 and to their respective side nozzles25 and 26. However,

at periods of slower traffic, a switch will be thrown to actuate one ofthe air cylinders 106 to pull its piston rod 107 inwardly to rotate therod 102 and damper flap 101 through the crank 108. For instance, thedamper flap 101 would be pivoted to its blocking position within theside unit 21, and the damper flap 101 for the side unit 20 would be inits unblocking position. With the damper flap 101 for the unit 20 in itsunblocked position, the blower unit for the side unit 20 is forcing airacross the upper duct 22 to enter through the opening 79 into themufller 48 of the side unit 21. Because of the blocking position of thedamper 101, the high velocity air entering the muflier unit 48 throughthe top duct 22 and its opening 79 flows in the annular air space aboutthe inner cylindrical mufiier member 68 and out opening 80 in outermuflier member 75 and through the side duct 82 to the side nozzle 26 forthe side unit 21. Thus, it will be seen that the side unit 20 is capableof providing air not only to the top nozzle 24, but to both of the sidenozzles 25 and 26. If it were not for the damper flap 101, the forcedair entering the muffler 48 from the top duct 22 would flow through thebore of the inner muflier 68 and through the duct 62, and in turnthrough the impeller and then outwardly the air intake 42 to atmosphere.Hence, the closing of a damper flap 101 prevents the exhausting of highvelocity air from one of the side units through the air inlet of itsopposite side unit and diverts high velocity air through the muffler andopposite side nozzle of its opposite side unit to the side of caropposite its own muflier and side nozzle.

It will be appreciated that the ability to employ only one of twoelectric motors of a range of 30 to 80 HP can result in a significantsavings in the amount of power required and thereby reduce operatingexpenses considerably. Also, the preesnt invention is adapated to reducethe power requirements for a blower unit to produce the 250 mph. or moreair velocity, 20 ounces of static pressure, and 16,600 c.f.m. at an airdrying station for a car wash line.

More specifically, the conventional dryer units have employed 120 to 140HP to produce air at the rate of 1,660 c.f.m. at 250 mph. By an improvedimpeller design, the present invention has been found to reducehorsepower of the impeller motors by about 30% for an installationcorresponding in size to a prior art installation. In the presentinvention, as best seen in FIG. 9, the cross section of the impellerblades 120 is changed from that of the normal fiat blade heretoforeemployed to a blade having an air foil working surface 121. Preferably,the blades 120 are hollow aluminum blades with central cavities 122 and123 therein to reduce the weight. Tlhree tapped openings 124 are formedin the ends of each blade 120 to receive screw type fasteners 125 whichsecure the opposite ends of the respective blades 120 to impeller sideplates 126 and 127, respectively.

The air foil surface 121 has a greater curvature than the bottom surface130 of the same blade, the bottom surface 130 being practically flat orhaving a slight curvature thereto. The general path of air flow from thecenter of the impeller as shown in FIG. 9 as being free from the centralportion outwardly along the air foil surface 121 and between the rearsurface of the preceding blade in the direction of rotation DA, FIG. 9.In accordance with well-known theory, the stream of air moving across anair foil surface 121 is forced to flow through a constricted area andits speed is increased while the air at a higher level above the airfoil surface is not so constricted. An area of less pressure is formedabove the blade 120 than below the blade 120 giving the typical lift asin airplane wing air foil surface. The air foil surface reduces airturbulence at the outer ends of the impeller blades 120. The relativeefliciency of the impeller employing blades 120 having an air foilsurface 121 is markedly pronounced and has been found to be increased bythe surprising amount of approximately 30% in some applications.

As seen in FIG. 8, the driving shaft for the motor has secured thereto acircular plate to which is secured an inclined plane coupling 141. Theinclined plane coupling 141 has an outer flange 142 with an innerinclined surface 143 adapted to be in mating engagement with 'aninclined surface 144 of an inner bushing 145. The flange 142 and bushing145 each are half threaded with mating threads at selected spaces on theinclined surfaces 143 and 144 to receive threaded screws 148. The screws148, upon being turned in one direction in the threads force the bushing145 leftwardly as viewed in FIG. 9, to be clamped more tightly to themotor shaft. While not shown, it is to be understood that the bushing145 has a slit extending 'axially through its body so that the bushingcan be forced to have a smaller inner diameter as its surface 143 isforced leftwardly along the inclined surface 144 by the screw 148.

From the foregoing, it will be seen that the present invention isparticularly adapted to reduce the power requirements for an air dryingstation by increasing the blower efficiency by employing impeller bladesin the blower, having an air foil working surface to drive the air.

Also, it is noted that the present invention provides the reduction ofexpense by affording a drying system adapted to be varied for heavy dutyor light duty traffic by selectively enabling a blower unit to supplyair to either one side nozzle or to both side nozzles, as well as to atop nozzle. More specifically, the present invention employs dampermeans to permit the flow of air from one blower unit across a top ductand into the side nozzle, at the opposite side of the automobile, Whilea damper means is blocking the exist of the high velocity air out theair intake for the idle blower unit.

Hence, while preferred embodiments of the invention have been describedand illustrated, it is to be understood that they are capable ofvariation and modification.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Dryer apparatus for installation in an automobile car washing unit tosweep air across each side of a vehicle and across the top of a vehiclemoving through said washing unit, said dryer apparatus comprising afirst blower unit disposed on one side of the pat-h of movement of thevehicle and adapted to produce a stream of air under pressure through afirst outlet in fluid communication with the first blower unit fordrying the vehicle, a first side nozzle means in fluid communicationwith and receiving air from the outlet of said first blower unit toapply air to the first side of the vehicle, a second blower unitdisposed on the other side of said path of movement of said vehicle andadapted to produce air under pressure through a second outlet in fluidcommunication therewith for drying said vehicle, a second side nozzlemeans in fluid communication with the outlet of said second blower unitand adapted to apply air to the other side of said vehicle, a duct meansextending above the path of movement of said vehicle and in fluidcommunication with the outlet of each blower unit, a top nozzle means insaid duct means adapted to receive air from the outlet of each of saidfirst and second blower units to sweep air across the top of a vehicle,means for operating the blower units in unison at times of heavy trafficand for disabling one of the blower units at times of light traffic, andselectively operable control means for diverting air from the operativeone of said blower units through the outlet of the opposite blower unitand the corresponding side 'and top nozzle means associated therewithwhen said opposite blower unit is disabled for periods of light traffic,said selectively operable cor'i trol means including damper means forblocking a portion of the outlet leading to communication with thedisabled blower unit.

2. Dryer apparatus for installation in an automobile vehicle car washingunit to sweep air across offset sides of a car and across the top of acar along a path moving through said car washing unit, said dryerapparatus comprising a first blower unit disposed on one side of thevehicle path and adapted to produce a stream of air under pressure fordrying the automobile, a first muflier means connected to said firstblower unit to dampen the noise of its air stream, a first side nozzlemeans receiving air from said first mufiier means to apply to one sideof an automobile, a second blower unit disposed on the other side ofsaid path of movement of said vehicle adapted to produce a stream of airunder pressure for drying the other side of said vehicle, a secondmuifier means connected to said second blower unit to dampen the noiseof its air stream, a second side nozzle means in fluid communicationwith said second mufiier means and adapted to sweep air across the otherside of said vehicle, a duct means extending across the path of movementof said vehicle and connected to said first and second muffler means, atop nozzle means in said a duct means adapted to receive air from saidfirst and second rnufiler means to sweep 'air across the top of avehicle, and selectively operable control means for diverting air fromone of said blower units through its opposite blower unit, andcorresponding nozzle means when said opposite blower unit is disabledfor periods of light traffic.

3. The dryer apparatus of claim 2 wherein said control means includes adamper means disposed in each of said mufiier means, each of said dampermeans being selectively positionable to block flow of air from said ductmeans to its connected blower unit and to divert the flow of air to itsconnected side nozzle means so that a blower unit can supply 'air underpressure to the other side nozzle means without exhausting air throughthe opposite, disabled blower unit.

4. The dryer apparatus of claim 3 wherein said first and second muffiermeans include spaced inner and outer cylinder means of differentdiameters and different lengths, each of said inner cylinder means beingconnected to its respective air blower unit, each of said outer cylindermeans being connected to its respective side nozzle means and alsoconnected to said top nozzle means, each of said damper means disposedin its associated inner cylinder means to block flow of air enteringfrom said duct means to its associated blower unit when its associatedblower unit is disabled.

References Cited UNITED STATES PATENTS 1,246,090 11/1917 Hagen 230-1342,663,951 12/1953 Kennison 34-233 2,758,392 8/1956 Vani et al. 342292,874,485 2/1959 Wilson 34-230 3,128,161 4/1964 Hudon 34233 0 FREDERICKL. MATTESON, JR., Primary Examiner.

A. D. HERRMANN, Assistant Examiner.

1. DRYER APPARATUS FOR INSTALLATION IN AN AUTOMOBILE CAR WASHING UNIT TOSWEEP AIR ACROSS EACH SIDE OF A VEHICLE AND ACROSS THE TOP OF A VEHICLEMOVING THROUGH SAID WASHING UNIT, SAID DRYER APPARATUS COMPRISING AFIRST BLOWER UNIT DISPOSED ON ONE SIDE OF THE PATH OF MOVEMENT OF THEVEHICLE AND ADAPTED TO PRODUCE A STREAM OF AIR UNDER PRESSURE THROUGH AFIRST OUTLET IN FLUID COMMUNICATION WITH THE FIRST BLOWER UNIT FORDRYING THE VEHICLE, A FIRST SIDE NOZZLE MEANS IN FLUID COMMUNICATIONWITH AND RECEIVING AIR FROM THE OUTLET OF SAID FIRST BLOWER UNIT TOAPPLY AIR TO THE FIRST SIDE OF THE VEHICLE, A SECOND BLOWER UNITDISPOSED ON THE OTHER SIDE OF SAID PATH OF MOVEMENT OF SAID VEHICLE ANDADAPTED TO PRODUCE AIR UNDER PRESSURE THROUGH A SECOND OUTLET IN FLUIDCOMMUNICATION THEREWITH FOR DRYING SAID VEHICLE, A SECOND SIDE NOZZLEMEANS IS FLUID COMMUNICATION WITH THE OUTLET OF SAID SECOND BLOWER UNITAND ADAPTED TO APPLY AIR TO THE OTHER SIDE OF SAID VEHICLE, A DUCT MEANSEXTENDING ABOVE THE PATH OF MOVEMENT OF SAID VEHICLE AND IN FLUIDCOMMUNICATION WITH THE OUTLET OF EACH BLOWER UNIT, A TOP NOZZLE MEANS INSAID DUCT MEANS ADAPTED TO RECEIVE AIR FROM THE OUTLET OF EACH OF SAIDFIRST AND SECOND BLOWER UNITS TO SWEEP AIR ACROSS THE TOP OF A VEHICLE,MEANS FOR OPERATING THE BLOWER UNITS IN UNISON AT TIMES OF HEAVY TRAFFICAND FOR DISABLING ONE OF THE BLOWER UNITS AT TIMES OF LIGHT TRAFFIC, ANDSELECTIVELY OPERABLE CONTROL MEANS FOR DIVERTING AIR FROM THE OPERATIVEONE OF SAID BLOWER UNITS THROUGH THE OUTLET OF THE OPPOSITE BLOWER UNITAND THE CORRESPONDING SIDE AND TOP NOZZLE MEANS ASSOCIATED THEREWITHWHEN SAID OPPOSITE BLOWER UNIT IS DISABLED FOR PERIODS OF LIGHT TRAFFIC,SAID SELECTIVELY OPERABLE CONTROL MEANS INCLUDING DAMPER MEANS FORBLOCKING A PORTION OF THE OUTLET LEADING TO COMMUNICATION WITH THEDISABLED BLOWER UNIT.